Patent Document 1 describes an example of a known vehicle seat sliding device. The device includes two lower rails, two upper rails, and a block body. Each of the upper rails is coupled with a corresponding one of the lower rails in a movable manner. The block body prevents a foreign object that has entered the rails from being entrapped. A bolt for fixing each lower rail to a vehicle floor is provided rearward from the block body. The block body, which is arranged on a bottom wall of the lower rail, has a slanted surface that gradually rises toward the bolt. When a foreign object enters the rails in front of the block body, as the upper rail moves toward the rear, the foreign object is pushed and moved by the upper rail. This gradually raises the foreign object along the slanted surface of the block body. Accordingly, the foreign object pushed by the upper rail passes over a head of the bolt, which is arranged rearward from the block body. This prevents the foreign object from being entrapped between the upper rail and the head of the bolt.